Compartmented suction box



Sept 15, 1964 w. c. MIH 3,149,027

COMPARTMENTED sUcTIoN Box Filed June 11, 1962 2 sheets-sheet. 1

INVENTOR.

A TTORNE YS W. C. MlH

COMPARTMENTED SUCTION BOX Sept. 15, 1964 2 Sheets-Sheet 2 Filed June l1, 1962 Rw S f A k f M y United States Patent O 3,149,027 CMPARTMENTED SUCTIN BOX Walter C. Mih, South Beloit, lil., assigner to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed June il, 1962, Ser. No. 201,406 11 Claims. (Cl. 162-268) The present invention relates to improvements in a mechanism and method for obtaining an improved paper web of uniform thickness on a Fourdrinier paper forming machine.

In a Fourdrinier machine paper stock is discharged onto the travelling Fourdrinier forming surface from the slice of a head box and water is drained from beneath the wire by drainage means including suction dat boxes. A visible dryline will appear on the surface of the paper web extending across the Fourdrinier wire at a location down ahead of the couch roll. The papermaker usually will adjust the slice opening to obtain a straight dryline on the assumption that the straight dryline indicates that a web of uniform thickness is being formed because uniform drainage is being obtained to provide the straight dryline.

However, the drainage rate varies as a function of a number of other factors which vary drainage resistance including Wire wear, mechanical variations, vibration, showers, and so forth, and these factors are often hard to eliminate or equalize so that uniform drainage occurs across the Fourdrinier machine. It has been discovered that there is a difference in drainage resistance among various spots on the same worn Fourdrinier wire and that the wire at the low basis weight point has a lesser resistance to ow than the wire at a higher basis weight point, and organic deposits, fibers and so forth will also tend to vary the drainage resistance. When the dryline begins to deviate from the straight line, the machine tender usually adjusts the slice lip opening to compensate the drainage difference on the wire until the dryline becomes straight. However this adjustment will cause a paper Weight variation across the machine.

It has been shown that the unit discharge of the slice is proportional to its opening size. Where:

h is the pressure at the slice in feet of water, V is the velocity of jet, f.p.s.

d is the slice opening,

T is the thickness of jet.

CV is a function of the geometry of the approach channel and varies within a narrow range. On paper machines, the adjustment of the slice, compared to other dimensions of the head box is small. For a certain head box :the variations of C,y will be very small too and this means that under the same pressure, the velocity is constant regardless of the slice opening. The unit discharge q? VT=q=CcdV=Ccd constant C,3 is the coefcient of contraction, which in the case of most paper machines does not vary appreciably with the slice opening and therefore:

q=constant X d In accordance with the present invention the slice lip at the head box is adjusted to provide for a uniform delivery of stock completely across the wire. The slice lip adjustment provides a constant ratio of fiber to water which provides a constant liber quantity.

Any variation in moisture in cross machine direction which may occur is then a function of the variation in wire drainage characteristics. Such moisture variation Frice can be spotted at the dryline on the Fourdrinier. This dryline usually occurs between the third and fourth iiat box.

Accordingly, an object of the present invention is to provide a mechanism and method wherein a uniform stock delivery is maintained completely across the Four.- drinier machine, and a control of water drainage or suction at dilerent lateral locations is obtained to compensate for unequal drainage factors across the machine.

A further object of the invention is to provide a mechanism and method whereby a variable drainage force is applied across the machine which is regulated until a straight dryline is obtained.

A still further object of the invention is to provide a compartmented hat box extending across the machine With dilierent compartments being controllably subjected to different suctions for providing a compensating drainage and obtaining a straight dryline.

Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings in which:

FIGURE l is a schematic side elevational view of a Fourdrinier machine embodying the principles of the presen-t invention;

FiGURE 2 is a vertical sectional view, shown in schematic form, taken substantially along line II-II of FIG- URE l;

FEGURE 3 is a top plan view shown in schematic form of the mechanism of FIGURE 2;

FIGURE 4 is a fragmentary schematic View showing a portion of an arrangement similar to FIGURE 2 but of modified form;

FIGURE 5 is a fragmentary top plan View taken substantially along line V-V of FIGURE l;

FIGURE 6 is a schematic fragmentary top plan View of another form of compartmented suction box; and

FIGURE 7 is a schematic top plan view of a further modiiied form of compartmented suction box.

As shown on the drawings: s

FIGURE 1 illustrates a paper web W being formed on a travelling Fourdrinier Wire 10 supplied with stock from the head box 11 having an adjustable slice 11a. In accordance with the principles of the present invention the slice 11a is maintained at a size for providing a uniform delivery of stock completely across the machine and is not regulated or changed nonuniformly at different locations when variations in the dryline occur.

The Fourdrinier wire 10 is carried on a breast roll 12 at one end and a couch roll 13 at the other end and the paper web is picked off by a pickup felt 14. The Fourdrinier travels downwardly around the return roll 15 and over guide rolls 16.

Beneath the upper run of the Wire 10 are table rolls 17 and a series of suction dat boxes. Suction ilat box 18 is shown followed by a compartmented suction at box 2.0 which is followed by additional suction flat boxes 21 and 22a, with the at boxes 18, 21 and 22a being of conventional design and structure.

The compartmented suction flat box is shown in greater detail in FIGURE 3 and has longitudinally extending separators or Walls such as 19 to divideV the flat box into compartments such as 23 and 24.

In accordance with the method of the invention, the compartmented flat box 20, FIGURES 1 and 5, is positioned ahead of the dryline L, and the method embodies the step of applying a controlled variable suction beneath the wire ahead of the dryline to compensate for Variations in drainage resistance. In other words, means are provided extending across the wire for applying a controllable suction force or for varying the drainage rate across the wire in order to obtain a straight dryline.

Each of the compartments of the suction box Ztl are connected to separate drainage lines 22, shown by the individual drainage lines 25 and 26 for the compartments 23 and 24. The drainage lines lead to a suction source 29 which is shown as being in the form of a separator connected to a downwardly depending drop leg at its lower end and attached to a vacuum manifold at its upper end.

Each of the drain lines must be sufficiently large so as not to become stopped during operation, inasmuch as stoppage would terminate suction in the individual compartment to which the drain line is connected and have very undesirable results. In each of the drain lines is connected a pressure regulating valve, as illustrated by valves 27 and 28 for the lines 25 and 26. These valves may take various forms to regulate the suction in the compartments to which the individual lines lead, and may be in the form of valves limiting the opening in the line a1- thoughas previously stated the valve must be of such a nature that the danger of stoppage is eliminated.

In another form, as illustrated in FIGURE 4 by the suction box compartments 23 and 24 lead to drain lines and 26 and valves 49 and 41 are in the form of air bleed Valves which bleed ambient air into the lines and thereby reduce the pressure in the individual compartments. This reduces the chance of stoppage in the lines since a completely open line may be employed Without being impeded by valves which close part of the line passage. Various other arrangements may be employed for controllably varying the suction in the different compartments so that each compartment is provided with the suction desired to obtain a straight dryline L.

As illustrated in FIGURE 5, when the machine is operating and the slice is set to deliver uniform stock across the machine, the dryline L may take a nonuniform appearance, the valve lines 22 are then adjusted to vary the suction in the compartments 20 until the dryline L extends substantially straight laterally across the machine.

T o avoid encountering a visible line of demarcation between suction compartments on the paper web, the walls between the compartments may be positioned so as to be nonparallel to the direction of web travel. This is illustrated in FIGURE 6 by the suction box 30 wherein the compartment 33 is bounded by walls 31 and 32, and the wall 32 extends between the compartments 33 and 34. Web travel is of course normal to the suction box 39, and the walls 31 and 32, as Well as the other Walls of the box between the compartments extend at an angle to the direction of web travel, and substantially triangular compartments are formed.

In the at box 35 of FIGURE 7, compartments 36 and 37 are illustrated, and the compartment 36 is bounded by compartment walls 3S and 39 which are at an angle to the direction of wire and web travel, and the wall 38 extends between the compartments 36 and 37. Compartments which are substantially trapezoidal in shape are formed.

Thus it will be seen that I have provided an improved suction fiat box and method of operation of a Fourdrinier machine which meet the objectives and advantages above set forth. A new method is provided for regulating the dryline so that the machine tender Will not erroneously have to change the dimensions of the slice lip across the machine to compensate for changes in dryline. Once a uniform delivery is determined, changes in slice size Will not be made and in accordance with the principles of the present invention change in shape of drylines will reflect a variation in drainage rate due to drainage factors of the machine and not due to improper stock delivery. Nonuniform drainage is corrected by applying a correcting drainage factor which provides for increased drainage at zones of slow drainage, and for decreased drainage at zones of rapid drainage, therefore resulting in uniform Water removal by the time the web reaches the dryline so that a uniform straight dryline can be obtained.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

I claim as my invention:

l. In a Fourdrinier paper machine the combination comprising a travelling Fourdrinier wire having a forming surface, a head box for depositing stock on the wire, suction Hat boxes beneath the wire for removing Water from a web formed on the wire surface, a compartmented flat box beneath the wire positioned ahead of the dryline of the web formed on the wire having separate suotion compartments at different locations across the web, means for applying suction to each of said compartments, and means for controlling the suction in each of said compartments so that a straight dryline can be obtained.

2. In a Fourdrinier paper machine, the combination comprising a travelling Fourdrinier wire providing a forming surface, a head box for depositing stock on the Wire, suction dat boxes beneath the wire for removing Water from a web formed on the wire, a compartmented fiat box beneath the wire positioned ahead of the dryline of the web on the Wire and having separate suction compartments at different locations across the wire, means for applying suction to each of Said compartments, and individually controllable suction lines leading to said separate compartments so that the suction at different locations can be regulated.

3. In a Fourdrinier paper machine, the combination comprising `a travelling Fourdrinier wire providing a forming surface, a head box for depositing stock on the wire, and means for applying different suctions at different lateral locations beneath the wire, said suctions being selectively variable at said different locations.

4. A mechanism for obtaining a straight dryline in a Fourdrinier paper machine having a travelling Fourdrinier wire and a head box for depositing stock on the wire, said mechanism comprising means positioned beneath the Wire for draining Water from the web on the surface, said means operative to remove Water at different rates at different lateral positions across the Wires, and means for controlling the rate of water removal at said different positions so that a straight dryline can be obtained.

5. In a Fourdrinier papermaking machine having a head box feeding stock onto a travelling Wire and suction iiat boxes beneath the wire, the improvement comprising means extending across beneath the Wire for applying a suction beneath the wire having means for controllably regulating the suction at different locations across the wire so that different suction forces may be applied at diferent lateral locations for obtaining a straight dryline.

6. A Fourdrinier papermaking machine comprising a Fourdrinier Wire, a Fourdrinier bed having rolls supporting the wire thereon, a plurality of main suction at boxes on the bed beneath the wire, a compartmented suction flat box between said main at boxes extending laterally across beneath the wire having a plurality of individual compartments positioned laterally of each other, means for applying suction in the compartments and means for controlling the suction in said individual compartments.

7. In a Fourdrinier paper machine the combination comprising a travelling Fourdrinier wire having a forming surface, a head box for depositing stock on the wire, a compartmented at box beneath the Wire having separate suction compartments at different locations across the Wire, a suction source, individual lines leading from said separate compartments to said source, and separate bleed valves in individual lines to bleed ambient air and reduce the suction in individual lines.

8. In a Fourdrinier paper machine, including a travelling Fourdrinier Wire having a forming surface, a head box for depositing stock on the wire, means for draining water from the stock on the wire, and a plurality of suction compartments at dilerent locations across beneath the Wire for draining Water from a web formed thereon and being individually regulatable as to suction applied to the wire, the improvement wherein said compartments have lateral edges extending nonparallel to the direction of travel of the wire.

9. In the method of obtaining a paper web of uniform thickness on a Fourdrinier machine including feeding stock onto a traveling Fourdrinier wire in a uniform quantity across the wire, and applying a controlled suction beneath the Wire ahead of the dryline, the improvement comprising controllably varying the suction at different lateral locations for obtaining a straight dryline.

10. In the method of obtaining a paper web of uniform thickness on a Fourdrinier including feeding stock onto a traveling Fourdrinier Wire in a uniform quantity across the wire, the improvement comprising controllably varying the suction applied beneath the Wire at different lateral locations as a function of the curvature of the dryline until a straight dryline is obtained.

11. In a method of dewatering a paper web on a Fourdrinier wire formed by feeding stock onto the travelling Fourdrinier Wire, the improvement comprising controllably varying the drainage rate of the Water from the Web formed on the Wire at different lateral locations across the wire for obtaining a predetermined dewatering characteristic across the wire.

References Cited in the ile of this patent UNITED STATES PATENTS 1,833,351 Berry Nov. 24, 1931 2,893,486 Marti July 7, 1959 2,990,014 Hornbostel June 27, 1961 FOREIGN PATENTS 1,116,448 France Feb. 6,1956 

1. IN A FOURDRINIER PAPER MACHINE THE COMBINATIN COMPRISING A TRAVELLING FOURDRINIER WIRE HAVING A FORMING SURFACE, A HEAD BOX FOR DEPOSITING STOCK ON THE WIRE, SUCTION FLAT BOXES BENEATH THE WIRE FOR REMOVING WATER FROM A WEB FORMED ON THE WIRE SURFACE, A COMPARTMENTED FLAT BOX BENEATH THE WIRE POSITIONED AHEAD OF THE DRYLINE OF THE WEB FORMED ON THE WIRE HAVING SEPARATE SUCTION COMPARTMENTS AT DIFFERENT LOCATIONS ACROSS THE WEB, MEANS FOR APPLYING SUCTION TO EACH OF SAID COMPARTMENTS, AND MEANS FOR CONTROLLING THE SUCTION IN EACH OF SAID COMPARTMENTS SO THAT A STRAIGHT DRYLINE CAN BE OBTAINED. 